Caroliano

How accurate are this OTRAG parts. Are they balanced for the real solar system or the vanilla game? The thing that interests me most in that rocket is the unique (?), dead simple, pressurization system it uses. The tanks are filled with 40 bar air, then emptied until the pressure is 15 bar (also serving as a test for the valves and such), then the fuel and oxidizer are injected till they fill 2/3 of the tank and the pressure go back to 40 bar. Then, during the course of the burn, the tank/injector pressure drops from 40 to 15 bar, and as consequence the chamber pressure drops along from 30 bar to 10 bar. That provides natural throttling to limit the Gs and at the same time does not cause problems like flow separation or too big of an isp drop because the outside pressure drops much faster than the internal one. That is a very interesting dynamic and is the main reason I want to fly one of those rockets. In addition to that, the single valve controlling the fuel and oxidizer flow has 3 positions: 100%, 40% and closed. Those percentages are of the maximum thrust at that point in the burn, so in the end it can be throttled to 13.3...% of the initial thrust. The reason the third and last stage has 4 modules is because the pitch and yaw would be controlled by throttling or shutting down individual engines (for roll, they would use cold gas thrusters). I see that in the arrangement in your add-on the last stage is composed of a single module (to make it lighter to the physics engine?). How does your add-on handles pitch and yaw? Simple magic ksp reaction wheel? That is not actually that important for me, but would be cool to have as well as an realism option. Finally, it would be cool to have different options on the length of the modules. I assume you have this material, but dropping the link anyway: PDF about OTRAG

Let's list what is wrong: * Hipothetical 10+km mines don't change the fact that virtually all mines in earth are <1km and a 3km mine is already a technological and cost challenge. Mining better scales to surface size. * 10km is still scratching the surface even on kerbin. Volume doesn't matter. On mini-kerbin it depends on the depth of the crust. * I bet your "estimated year when it runs out on earth" don't account for "over 10km or deeper" mining, so you shouldn't be counting for all that volume. * I would be interesting to plot "Estimated year when it will run out" with time for earth. Those numbers have been going up as we find new mines or the rise in the resource's price or new technology makes new mining technology economical. This should happen in kerbal too, even more rapidly. Though "over 10km or deeper" isn't terrible precise and I never heard about such concepts. Are they more advanced than space elevator concepts? Ok, then re-run your calculus with, say, 80% recycling. Metals are relatively easy to recycle. The higher it's price the better. And you can bet that metals being mined 10km deep are pretty pricey.

See the study I linked. Some would call they useless already beyond Jupter orbit. The study projects that 400W power generation in Uranus would weight 781kg in solar panels (you can round up to 1 ton). A lot, but still feasible. Just to put in perspective, that same solar power array would generate 232kW on earth's orbit. So, about 500 times less efficient on Uranus.

Interesting. I have not been following this, but this seems the second solar powered probe to Jupiter. I was assuming that we were still using RTGs for those probes, which is why I suggested a unified probe for Jupiter and beyond. Researching a little, it seems solar power is being considered even for Uranus missions (Source). Solar power for those missions seems to make things cheaper but heavier. But I believe that the main thing we should always optimize for is cost so it is a good direction. A sedna probe would need to use RTGs though so it is kinda off-topic... I still think we could reduce the price and danger of making and manipulating RTGs with scale, as we would be able to automatize more of it. It is easier to justify constructing machines to help the montage of 20+ crafts than a single one. Space crafts aren't costly by magic, it is because each need many, many qualified human hours of work. We don't need super-heavy rockets for those deep-space probe missions. What we need is in-orbit refueling technology that could be developed for much less (and should be developed regardless). Just launch the probe and the empty booster stage (maybe in two separate launches if necessary) to LEO in medium-lift rockets, and then launch a few refueling missions to fill it up. Bonus points if you make this booster stage an reusable tug for the 20+ missions we should be doing, thus reducing the unit cost even more.

In a related question, how much delta-v would be needed to enter in orbit of sedna, as opposed to a flyby, in 10~15 years of travel time? Accounting for the much lower than ideal thrust of ion engines and possibly a Jupiter gravity assist. Has anyone done this calculation? I guess it is probably the most challenging out of all round bodies on our solar system because the distance (and thus time constraints) and lack of atmosphere. I can only find delta-v figures for traditional hohmann transfers, where it surprisingly don't seems the hardest thing to get an orbit for IIRC.

Can't we make a standartized orbital probe for objects from Jupiter onwards and "mass-produce" it? There are lots of places to go, and it should reduce the costs by some.

That someone was their team while working on HOTOL. Then when the British goverment pulled the funding it also seems to have used the Official Secrets Act to turn those patents secret (I'm not sure how it works) and now they can't use it.

I'm not sure what you are answering to. What I didn't remember is why the helium is used at all, besides HOTOL patent avoidance. In there hydrogen was used to cool the air directly.

You are missing magnemoe and SargeRho answers: the hydrogen is the one that cools that helium (for patent avoidance as well for a technical reason I forgot) You need about 6 times more heat to rise 1°C on 1kg of hydrogen than methane. So, much more. Methane is the most advantageous early in the flight for a regular rocket, because you can get better TWR and lower volume helps with the aerodinamic losses. But skylon don't need those high TWR on take-off, as it does so horizontally, and the lower volume it occupies is actually undesirable in skylon: it would require a complete redesign of the hypersonic/re-entry aerodinamics of the spacecraft, and I'm not sure if it is even possible. For the late part of the flight, where you don't need to cool the incoming air anymore, the higher ISP of hydrogen wins hands down on performance over methane. Methane isn't viable for skylon for various reasons. EDIT: A simplified view of the cooling system:

Thanks, it indeed went all right when I tried to install only mechjeb and kerbal engineer aftewards. I have not checked if there is any file left around, but everything is working as it should at least. I was only a little scared by the "unhandled" part.

Yeah, just done it. I'm now basically in the same point as I was with hard mode, but I got most of the money to upgrade the VAB basically by doing a 4 passenger sub-orbital ferry (3 missions in one, thanks to the upgraded mission control that I didn't had on hard and thus could only carry 3 passengers) and an orbital mission, testing some parts on the way. However, I'm going to upgrade the tracking center first for a moon flyby that I hope I can do with 30 parts including plenty of science instruments. The penny counting on hard mode had it's charm, but being virtually locked on lv1 buildings was becoming too limiting. I will enjoy the game on normal mode now, thanks. Latter I plan to run with realism overhaul, that seems the right kind of hard.

"Disk Full" is an unhandled exception. The program exited. I don't know if it is safe to continue the installation now that I have made free space.

Playing KSP again after a long time away. I chose the hard mode in the carrier mode, and all was going well until I discovered that I needed to upgrade the buildings, and the price for that is too high. Well, I got to orbit, but I'm already very handicapped with mostly lv 1 buildings. I can't imagine the amount of grinding necessary to upgrade the VAB, and grinding is not fun... Science and reputation are ok, as is money overall except for buying the upgraded facilities. I think halving their cost would make the hard mode more balanced.

Just went there. Got a good laught with this.

A quote from February this year: Source

What about beamed microwave power from space solar panels? Is that plausible? Elon Musk has talked that he wants to make a supersonic electric plane in the future, but never gave details on how that might be possible. Also, there is the hyperloop idea, that is not quite a vactrain, as it needs a bit of air to work.

Just wanted to leave here an Elon Musk quote about this topic: He is really more a fan of re usability, and for that they need all the performance they can get reasonably

Tyler Raiz did a pretty accurate Apollo mission recreation with the Realism Overhaul mods:

Those contracts are difficult. I got: "Test TT18-A Launch Stability Enchancer landed at the Mun." Is I'm supposed to find a TT18-A Launch Stability Enchancer that is landed on the Mun, somehow attach to it, and then stage?

@allmhuran: I thought you were going to save a little landing delta-v and "stage" those external fuel tanks in a lithobreaking maneuver! That would be even more absurd than overheat staging!

I also had this problem auto-landing on Mun. I thought that it was because only 1 in 5 engines of the stage were firing (the others ran out of fuel), and mechjeb's autopilot wasn't using the right thrust number.

A revamp in the VAB interface is desperately needed IMHO. It is quite cumbersome to walk between pages. And of course the ability of saving parts of ships (launchers, satelites, etc), as already said.

Ok, commenting here is much better than in youtube. Basically repeating what I said in youtube: The pure parachute solution can be made to work. All parachutes need to be well above the center of mass of the vehicle, so they make the ship point up more effectively. Once you are pointing up, you can make a small burn to avoid break up when they fully open, if needed, as Scott said in the video. If you only want to get into orbit, you can do that with even less fuel and thus cut the weight of your lander by about 5 tons and still get 4800m/s delta-v. Of course, assuming the target planet/moon has the same delta-v requirement for getting into orbit: Old image: This is an old design I did (originally posted here, and no answer about the bug yet...) and it can be improved by removing the top decoupler, and maybe jettisoning the landing legs... PS: Also liked the SRB approach. That solid booster has the highest Isp from all rocket engines in KSP. Not sure if it is a balancing bug.

Tassyr: about the window, see my last post in this thread, in this page (including the quote).

Thanks. I saw the file, and indeed the stats display position was outside my screen. Editing it to a normal value made it appear again. The problem is that I can click and hold in the middle of the status display and drag it outside the window when runing KSP in windowed mode. Then, there is no way to drag it back, except by editing the .cfg. I must have done that earlier...